Computing system



Dec. 26, 1950 J, ALLEN I 2,535,250

COMPUTING SYSTEM Filed April 18, 1944 INVENTOR.

JA MES S ALLEN Patented Dec. 26, 1950 FOFZFICE This invention relates:to; a computing. system andxparticulaflw to; an electromechanicat.typecomputer fzor-per-forming zarithmeticai operaaions :such-ias squaring;square rooting;.-multip1ying:and

. 1.2 .in a; proposedcaleul'ation and which may be set at. a.predetermined-value byvariable resistance 10.This..energizingg-ldirect.-current. will be .reierredwto .asQii. I. An.alternating current .fof. .any

dividing. The.principahobjectwhtheainvention-j suitablefrequencysHchasAOO cycles per second is to provide a device of thischaracterwherein .torquerproducing currents relationshipssare relied.upon..-to -accomplish.the-.desiredrresult..

The,ecalculatorautiiizesrl a .dynamometenstype .issuperimposed on.current 2; by means of. trans- Iformer '23 .to.. provide .an.-.error.signal. A-second ldirect.curre'nt,w i2; which. may. represent a secondgiven..quantity.inf.the. (calculation. fiowsihrmigh meterrand a.dArsonvaL/typezmeterz having itheir.s movablecoil 9 Jof theidynamometerandis suit- .lrespective. movable: coils mounted on: a common :shaft,the; saidcmeters being .suppliedn-withr current so that the-torques.producedzin .thetwomov- .able:.coi1s..are opposed. Two-givemquantitiesin a 7. proposed arithmetical computation. .are. trans- -.=1

lated into two torquerproducingocurrents flowing .inthee-abovemeter-=circuits. Aa.g-third: .-curfrent, Twhich representarthe unknownmalueqtonbeide- -terininedrfippears in a :third. circuit toprovide. a

abImQcontr'oIIed. ,by..XariabIexeSiStance 25. I. The

mvalu'eafof ..thel.two.currents' .are visibly. indicated by, suitably.calibrated meters .2 I and ;26',- respectively.

5 .In adynamometer, the product 'oflthe two-.cur-

rents inland. i'zT through'the. separate cfoil's. multi- -pnea by" the.cosine... ofrtheiarigle of lthelplan'e .of movable coil .hi ithlthe.direction .of. themagnetic field.fluxisiproportional.to. the torquetending. to

-counten-torquewhich: .maintains;-the .rotatablew- ;.turn7 thelotriting'.coi1v and its associated shaft? I 0.

shaft in a substantially neutral position. ..Th e. accompanying@drawing. is a diagrammatic .view; shoLwinglthearrangemerrtofthetwometers, and the'associated' circuits. ..Referringto.thedrawing, a.dynamometer type meter 5. hasan iron..core 6 :.-jof-;.the.shape-.shownproviding-thensual airsgap and ariield {20114-0011- .sisting'ofwinding. 1. JArmov'able coil 9.-is disposed :inl-thefaingap.andrigidlymountedmn a rotatable .sh'aftlil 0.1. Rotatablelshaft'lllis-provided W-i-than I .indicatonll I.-,anranged to move .over a.,suitab1y calibratedsciale-ll 2, the scalehavmg a central: zero pointcorresponding-to. a=no -coup1i ngvposition of coil .9- with respect}vto'..'the. field oi winding 1. A. d Arsonval. type m-eter. .is-.indicated ';;by l5; ThisJnetencomprises a.fixed--:permanent magnet ll 6.and atmovable. coil- I 1:.dis'posed b'etweens the \poles .of the magnetand. .mounted on. :above- -mentioned-.- shaft Ill. 1 A meter :2l 8indicates current through movamecoil ..l I... rthis currentiv repre-.-.senting" one. of. .th evalues;-. usua1ly .=the. unknown .value, inagivenz-problem.

v Field winding 1 ,of. the :dynamometer.---is .eonnectedminseries with.var'iablearesistancefifl a meter 22], .thetsecondary winding 22-.ofa;-trans- .former: 2.3; and. a. -source .of Da, f .130 t6htial-:24.Movable coil 9 of the same meterflaconnected rin 'serieswwitla avariable ;-resistance 25 armejter '26; .anda source lof D.. .C;.;potentia12 .,-..One:rside of this circuit rbeing grounded. aoutputriead like tends-.toiinputvterminal": tzzan' amplifier anddetectorasystemehereinaitervdescribed.

-a- Field winding leof iaher dynamometerrisqgenergized gbya;:direct:kcurrent whichwcorrespondsitoone-of:.thergiveniindependentiaquantitieainvoived Assuiningithati thedirect current(z'1 and i2) .con- .ditions ;inf..the..dynamometer producea torque, ani'alternating current...may be induced in movable coil 9by"the.alternatingoomponent present #25 in. the field.--..(.:oi1."circuit/l The amplitude of.the

inducedt'alternating .current will, of course, be gpnoportionairto' theangle betweenmovable coil 9 an the magnetiofield inlthe air. gap due toWind- Ling I. Theiresulting" alternating component in 0 LthemovablecoiLcircuit .(error signal) isapplied.rthrough1eadl29.toinput3l1ofan amplifier system.

The. amplifier .system comprises input .transformen'35,fwhich feedstheerror signal to vacuum 'Ltnbefamplifiei 36. having cathode .3], control.grid 5 '.-.38,and1an'ode39. 'GridiSB. is connected togroundthrough..by=pass.condenserIAO, and anode l39 is .-.conne'ct'ed,..to asuitablewsource of.- potential .;through.rdropjping resistance 4|..Cathode =31 is grounded through biasresistance 42 which.isbypassed.,by.cohdenser 43. A blockingcondenser 44 :is provided in theoutput circuit which. is grounded through load-resistance. 45.

Potentials developed across load resistance. are-applied to a-.second.amplifier .50 .having leath- 5- ode 5|, control grid 52 and anode .53.Thisamplifier-1is. -simi1arly. provided with cathode biasresistance.54..-by pass-.condenser 55, droppingre- .sistance 56,.b1ocking:. condenser '51 and grid" re- :sistance .58. fromwhich-.themitput is applied to amplifien-tube- 60.

..The. tube Z60. hasacathode .6 l, 'control grid '62, "screen grid63...and--anode- 64. Screen grid 63- is ..connected ..to thev anode-64",- .while -c.athode.6 I is :grounded: through-the; parallel:combination. of

i ancesfiiani kpass condenser 66.;: .An-

ode 64 is connected to its source of potential through the primarywinding of output transformer 61, which couples the output of the thirdamplifier stage to a detector tube 10.

Detector system I comprises two triodes, one having cathode I I, controlgrid 12 and anode I3, and the other having cathode l4, control grid Iand anode I6. The secondary Winding of output transformer 61 isconnected between ground and anode 18, this latter being connected tocathode II. Secondary winding 80 of transformer 23 is connected throughresistance BI across cathode I I and grid 12 of the triode.

Anode I3 is connected to cathode 14 and thence to one end of anothersecondary winding 85 of transformer 23. The other end of this secondaryWinding is connected through resistance 86 to control grid 15. Thepotentials on grids I2 and are sufficient to cause cut-oil on thenegative cycle. Thus potentials on the two control grids (fromtransformer 23) are in phase with each other and with the alternatingcurrent potential applied to the field coil of the dynamometer. Thevoltage (amplified error signal) applied through output transformer 61to the connection of anode I6 and cathode "I! may be either in phase orout of phase with the alternating voltage on the grids, depending uponthe direction of turning,

however slight, of coil 9 from its neutral position. I

If in phase, the top section I4, I5, and i6 is conducting and thedetected current is in one direction, while if out of phase, the lowersection is conducting, and the detected current is in the oppositedirection.

The pulsating detected current output from i.

Potentials developed across resistance 96 are applied to control gridI00 of vacuum tube IDI, this tube being arranged for cathode followeroperation. Anode I02 is connected to a suitable source of B+ potential,while cathode I03 is grounded through cathode resistance I04. outputpotentials from resistance I04 are applied through lead I05 to one endof movable coil H, the other end thereof being grounded through meterI8. This cathode follower stage is utilized to isolate the coil circuitfrom the amplifie and detector stages, as well as to provide animpedance match between them. Output lead I05 could, of course, beconnected to the positive end of any one of resistances 9B, 95, or 96and the cathode follower stage eliminated, if desired.

The detected current in movable coil ll of dArsonval meter I5 is ofappropriate sense and magnitude to provide an opposing torque by coilII. This current, designated as 2'3, is visibly indicated by meter I8.

Due to the amplification of the alternating current induced in movablecoil 9, it requires only a slight movement of coil 9 from its neutralposition, shown in the drawing, to produce a detected current throughmovable coil I'I. By proper proportioning of the meters and currentspassing through coil H, the torque generated by coil i! is just strongenough to balance the torque in the dynamometer due to the directcurrents therein. It should be noted that the alternating The currentsinduced in pick-up coil 9 are so small in value that no torque isproduced as a result of such currents.

In a dArsonval meter the torque developed by the movable coil isproportional to current (is) through the coil and the cosine of thedeflection angle away from neutral position. Similarly, in adynamometer, torque is proportional to the two currents involved (11 andi2) and the cosine of the same angle. As the movable coils in the twometers are maintained by the opposing torques very close to neutralposition, the cosines of the two deflection angles (0) are unity, orsubstantially so, and the following current equation may be written:

7 i1 i2=Ki3 where K is a constant of proportionality. This equationindicates the mathematical operations, i. e. squaring, square rooting,multiplying and dividing, possible with the calculator.

Since the entire system has both electrical and mechanical feedback, itis important that oscillations be prevented. This may be accomplished byelectrical damping in the amplifier stages or mechanical damping.

To perform a multiplication problem, for example, the multiplicand maybe set as the predetermined current (i1) through dynamometer field coilI, and the multiplier may be set as the predetermined current (i2) inmovable coil 9. The product, i1 times 2'2, is represented by the currentthrough movable coil I! of the dArsonval meter. If gain in the system isadjusted so that the proportionality constant is unity, the product maybe read directly on meter I8.

Potentiometers and for adjusting the currents in dynamometer coils I and9, respectively, may be optionally ganged together to facilitateoperations involving squaring or square rooting. I

Having thus described the invention, what I claim as new and desire tosecure by Letters Patent is:

1. A system of the character described comprising a dynamometer typemeter and a dArsonval type meter, means for rigidly coupling the movablecoils of said meters together, means for passing direct currents throughthe coils of said dynamometer meter, said means comprising separatecircuits for each coil and separate means for adjusting the current ineach coil to a predetermined value, said dynamometer coils undergoingrotation one with respect to the other due to said direct currents,means for impressing an alternating current on one of said dynamometercoils, means for amplifying and detecting only the alternatin potentialsinduced in the other dynamometer coil, means for feeding a currentthrough the dArsonval meter directly proportional to said detectedcurrent, for generating a torque in said dArsonval meter equal andopposedin direction to the force causing said dynamometer movable coilto rotate, and means for applying through said rigid coupling saidmechanical dArsonval meter torque to said dynamometer coil.

2. A system of two moving coil type meters comprising at least onedynamometer, means for mechanically coupling the moving coils of saidmeters, means for passing direct currents through the coils of saiddynamometer to rotate its moving coil away from its position of rest,said means comprising separate circuits for each coil and separate meansfor adjusting the current in each coil to a predetermined value, meansfor impressing an alternating current on one coil whereby an alternatingvoltage will be induced in the other coil of said dynamometer relativeto the displacement of said moving coil from its position of rest, meansfor detecting the alternating voltage in said other coil, meansresponsive to said detected voltage to energize a coil in the othermeter to mechanically restore the apparatus to a state of balance, andmeans for indicating the direct currents in each of said coils.

3. A mathematical product computer comprising an alternating currenttransformer having a primary stationary Winding and a rotatablesecondary winding, the normal relative position of said windings beingsuch as to prevent transformer action, said primary being energized froman alternating current source; two sources of direct current signal eachin circuit respectively with said primar and said secondary windings toefiect a rotation of said secondary relative to said primary and theinducing of an alternating current correcting component in saidsecondary, means for amplifying said correcting component connected tosaid secondary, said amplifying means including means for detecting therelative direction of rotation of said secondary as a function of thephase of said alternating current component with respect to the supplyfrom said alternating current source; a moving coil galvanometer havingthe coil thereof mounted on a shaft coupled with said secondary windingand a normal position of rest corresponding to that of said secondary;and means connected to be supplied from said detecting means, forapplying a signal to said moving coil in correspondence with thedirection and angle of rotation of said secondary from its normalposition, whereby said moving coil causes a torque to be applied to saidshaft tending to restore said secondary to its normal position.

4. A computer according to claim 3, and further including means incircuit respectively with said primary and secondary of said alternatingcurrent transformer for controlling the direct current flow in saidcircuits, and direct current indicator means in circuit respectivelywith said primary and said secondary of said alternating currenttransformer, and said moving coil of said galvanometer.

5. An electrodynamic system having a fixed and a movable portion, meansfor energizing said electrodynamic system, an electrodynamic balancenormally existing in respect to said fixed and movable portions, meansfor feeding two separate electric quantities into said system foreffecting an electrodynamic unbalance between said portions, saidmovable portion being caused to move thereby and a correcting signalvoltage being produced therein proportional to said unbalance, anelectro-mechanical system having a part mechanically coupled to saidmovable portion for mechanical control thereof, and means electricallysupplied from said electrodynamic system for feeding back saidcorrecting signal to said electro-mechanical system for effecting amotor action therein and a restoration of the balance of saidelectrodynamic system thereby.

JAMES S. ALLEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,907,804 Hausman et al May 9,1933 2,417,229 Alexanderson Mar. 11, 1947 OTHER REFERENCES Applicationsof the Electric Balance to the Continuous Solution of MathematicalFormulae," Borden, Instruments, Dec. 1929, pages 425-432

